Epigenome

This term of the biological sciences has been around for decades but it has been specialist, unknown to the general public. That changed to some extent in October 2009 when newspapers reported a paper that had appeared in the science magazine Nature.

We’re familiar these days with the idea that the nature of living things is controlled by the DNA in their genes, the genetic code of an individual being its genome. Since there are many sorts of cell, but only one genome in an individual, there must be a way to switch genes on and off inside the cell so that it develops into a specific type — fat, muscle, brain or other sort. This process is controlled by chemical switches collectively called the epigenome. The report in Nature was that researchers at the Salk Institute in La Jolla, California, had for the first time mapped it.

Environmental factors can disrupt the epigenome, which can lead to a variety of medical conditions, including cancers. Armed with the new roadmap of the way the epigenome works, specialists can now study the differences between healthy and diseased cells and begin to understand how this can happen.

Epigenome includes the prefix epi-, upon or in addition to, from Greek epi, upon, near to, or in addition to. Its study is epigenomics and the adjective is epigenomic. The field is new and the terminology is still evolving; it is common for researchers to use epigenetics instead of epigenomics for the study of all the changes to a cell that result from external rather than genetic influences.

The closely related term epigenesis refers to our current understanding that an embryo progressively develops from an undifferentiated egg cell, rather than the older belief that it is created completely formed (an homunculus) and merely grows bigger. The adjective epigenetic can refer to epigenesis, but is used in the scientific literature in connection with epigenomics.

Scientists believe the epigenome can be altered by environmental factors, ranging from diet to pollution, and disrupt this finely tuned regulatory process, setting the stage for various illnesses including cancer and heart disease.

The Globe and Mail, Toronto, 16 Oct. 2009.

The epigenome can be disrupted by smoking, ageing, stress, atmospheric pollution, what we eat and drink, and a host of other environmental factors. There is some evidence that the environment causes epigenetic changes that make people more susceptible to asthma.

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